Conventional check valves permit liquids or gases to flow in only one direction. Such check valves are present in hydraulic systems, typically in mobile and fixed equipment, to control the flow path of fluids in the system. Check valves are also used in a variety of pumps to prevent the backward flow of liquids.
The hydraulic system is typically connected to other, auxiliary systems that may share a common fluid path with the hydraulic system. When a leak or hose failure occurs in the hydraulic system, fluid may also leak from the other systems that are connected to the hydraulic system and result in further fluid loss as well as cause the auxiliary systems to fail.
It is therefore desirable to prevent the loss of fluid from the auxiliary systems when a fluid is lost from the hydraulic system.
Further, fluid losses in the hydraulic system may be exacerbated by the auxiliary systems. When, for example, there is a back pressure from the auxiliary systems, pressurized fluid reservoirs or the like, the fluid pressure from the auxiliary systems aggravate any leaks present in the hydraulic system.
Also, when there is valve leakage from the auxiliary systems, fluid will also be lost from the hydraulic system.
Thus, there is also a need to automatically isolate the hydraulic system from the accessory systems to further fluid loss when there is a leak in either the hydraulic system or in an auxiliary system.